Several individual cells have to be electrically conductively connected in series in a generator in order to generate energy by means of SOFC technology. The number of cells used then determines the electrical potential and thus the output of the generator. The output of the generator should ideally correspond to the total output of the individual cells.
A typical SOFC generator is developed from several sub units, the stacks. The stacks are combined from bundles with individual SOFC cells.
In the prior art, the individual SOFC cells are adhered to nickel contactings with the aid of a nickel epoxy resin, which is labor-intensive. For SOFC generators in the megawatt (MW) class, the total costs for the nickel epoxide and the processing thereof are considerable.
This adhesive system is also problematical in terms of controlling the layer thickness, in terms of a difficult and unmanageable application of the resin and a necessary curing time. The previous manual application is not possible on a large scale. A cost reduction aspired to for mass production can hardly be achieved with this type of contacting.
EP 1 786 056 A1 already discloses methods and materials for the electrical contacting of electrodes to interconnector layers in the case of solid electrolyte fuel cells, in which the materials are loosened in epoxy resins and are applied to the contact points. Tapes and/or transfer films can be used here.
Furthermore, a high-temperature fuel cell in the form of an SOFC is known from U.S. Pat. No. 6,379,831, which has tubular fuel cells, which are contacted to one another by way of metal weaves. Finally, this also relates exclusively to tubular fuel cells. WO 2005/117192 A1 discloses the conception of High Power Density (HPD) fuel cells and fuel cell systems developed therewith, in which the fuel cells consist of adjacent Δ or triangular shapes. Stacking such fuel cells realizes an adequate electrical contacting by adding metallic woven and/or knitted matting therebetween. Mat-shaped contactings are known for instance from DE 10 2004 047 761 A1, with the mechanical production of so-called knitted fabrics being detailed there, which are then folded into corresponding cushion shapes, for the purpose of using the cushion as elastic contactings between individual fuel cells.
As mentioned, the total costs for the nickel epoxide and the processing thereof are not insignificant for SOFC generators in the MW class. New approaches and/or alternatives are therefore sought in order to solve previous problems so as to be able to produce cost-effective SOFC generator systems.